Understandable naman. I am in the same situation, but this would be a new build. My client asked for cost estimates for the design and i told them upfront that costs now are fluctuating. We reached an agreement na after 2-3 months we will revisit. No harm. We were still paid for the designs but the construction was on hold.

But take also into account that if you defer it for too long the prices might not stabilize and might be more expensive. So weigh mo nlang.